<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #outer{
          width: 400px;
          height: 400px;
          background-color: aqua;
        }
        #center{
          width: 200px;
          height: 200px;
          background-color: red;
          margin: 0 auot;
        }
        #inner{
          width: 100px;
          height: 100px;
          background-color: blue;
          margin: 0 auto;
        }
      </style>
      <script>
        window.onload=function(){
          var outer=document.getElementById('outer');
          var center=document.getElementById('center');
          var inner=document.getElementById('inner');
          // 
          function handler(event){
            // console.log(event.target);
            // console.log(event.currentTarget);
            console.log(1);
            //阻止冒泡[DOM推荐标准(ie678不兼容)]
            //ie678用cancelBubble = true
            //兼容处理快捷键jr-zzmp/jr-stopPropagation
            // 阻止事件冒泡
            event.stopPropagation()
          }
          outer.onclick=handler;
          center.onclick=handler;
          inner.onclick=handler;
        }
      </script>
    </head>
    <body>
      <div id="outer">外部outer
        <div id="center">中心center
          <div id="inner">内部inner</div>
        </div>
      </div>
    </body>
    </html>